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This article investigates the effect of fiber orientation on forming and failure behaviors of a preconsolidated woven self-reinforced polypropylene (SRPP) composite during the stamp-forming process. Specimens with different aspect ratios were employed to study their formability during forming through a hemispherical punch in an open die configuration. The strain evolution in specimens was captured using a real-time strain measurement system (the aramis). A forming limit diagram (FLD), inspired from metal forming, was constructed to investigate the failure onset in the woven composite. The FLD revealed dominant failure mechanisms in [0 deg,90 deg] specimens were yarn splitting and fiber fracture as depicted by optical microscopy. A modified FLD was proposed to investigate failure mechanisms in [45 deg,−45 deg] samples. It was shown that delamination and intralaminar shear are the main causes of failure in this set of specimens. The outcomes of this study suggest that by changing forming parameters, such as fiber orientation, boundary condition, and aspect ratio, the formability of a preconsolidated SRPP can be improved. These results show the possibility of producing cost-effective, flawless, and fully recyclable products from consolidated woven composites. The proposed criterion can accurately predict failure in a woven composite by considering the combined strain interactions. This is reflected in the implementation of induced deformation modes and strain history into the failure criterion, making it a practical measure for rapid manufacturing techniques, such as stamping. The novel path-dependent failure criterion, introduced in this study, attempts to fill the gap for a reliable and accurate failure measure for woven composites.

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This paper presents the results of an investigation on stretch forming behaviour of two consolidated woven thermoplastic composites: a self-reinforced polypropylene (SRPP) and a glass-fibre reinforced polypropylene (GRPP) composite. A custom-built press with a hemispherical punch was employed to deform composites' specimens possessing different aspect ratios into an open die. The induced strains on the outer surface of specimens were measured continuously through two high speed, high resolution CCD cameras by employing a Digital Image Correlation (DIC) technique. The strain paths at three different locations on the surface of specimens were compared to elucidate the effect of fibre and matrix on the formability of a woven composite. The fractured surface of specimens was investigated to reveal the effect of fibre mechanical properties on failure morphologies in woven composites. It was found out that the main mode of failure in GRPP is fibre fracture while observed failure morphologies in SRPP were a complex combination of different failure mechanisms. It was revealed that the combination of applied boundary conditions and specimen's width determines the effective forming mechanisms.